1. Field of the Invention
The present invention relates to a method for producing a galactose transfer product.
2. Description of the Background
In recent years, attention has been directed to compounds which contain a galactose residue, especially transfer products of sugar (especially lactose), which can be used as a factor for the proliferation of Bifidobacteria (BIFIDUS, Vol. 2, No. 2, 1989). In addition, a change in physical properties such as increased solubility, or the like is noted in transfer products to sugar alcohols, nucleosides, alcohols, and the like. These transfer products are of high utilization value in their application to drugs, and the like.
A method which is known for producing galactose transfer products uses .beta.-galactosidase of E. coli. In the method the galactose residue is transferred to fructose or N-acetylglucosamine (Biotechnology Letters, 9, 243 (1987)) or the galactose residue is transferred to nucleosides such as adenosine, or the like. (Journal of Agricultural Association, Japan, 48, 605 (1979)). However, these methods have the disadvantage that the yield of transfer products production is poor. Another method for producing galactose transfer product (galacto-oligosaccharide), wherein the galactose donor is lactose and the galactose receptor is lactose, is known in which the .beta.-galactosidase of Aspergillus oryzae is used (Published Examined Japanese patent application no. 58-20266). However, the method is not very practical since the yield of galacto-oligosaccharide is poor. A need therefore continues to exist for an improved method of producing a galactose transfer product.